In an Orthogonal Frequency Division Multiplexing (OFDM) wireless communication system, two parties communicate with each other by transmitting OFDM symbols. OFDM symbols may interfere with each other while the OFDM symbols are being transmitted. For example, Inter-symbol Interference (ISI) commonly occurs in OFDM communication. In order to eliminate such ISI, a guard interval is typically interposed between two OFDM symbols.
The guard interval may eliminate the ISI but cause another interference such as inter-carrier interference (ICI). The ICI occurs because no signal is present during the guard interval and orthogonality between sub-carriers is interrupted. That is, ICI results since orthogonality between sub-carriers is not maintained during the interval. In order to eliminate the ICI, a cyclic prefix is inserted during the guard interval of a transmission frame. The cyclic prefix is typically a copy of a last portion of an OFDM symbol.
A length of a cyclic prefix may be determined based on delay spread that may be caused by multipath of a radio signal in a wireless communication environment. In a mobile communication environment, delay spread increases in proportion to a radius of a cell. For example, since a femtocell has a radius much smaller than that of a macrocell, delay spread of a femtocell is very small as compared to that of a macrocell.
As the cyclic prefix becomes longer, more resources including time and transmission power are required. Accordingly, a length of a cyclic prefix should be carefully designed according to a wireless cell radius. For example, if a cyclic prefix length was set up for a macrocell and a mobile terminal uses the cyclic prefix length for a femtocell without modification, time and transmission power is generally wasted.